Clinical genetic studies have shown that genes associated with specific autosomal recessive syndromes may be neoplasia-predisposing in the heterozygous condition. Estimates of the frequency of these heterozygotes in the general population have led to the conclusion that these genes are potentially important neoplasia-predisposing genes of man. For most of them, little is known of the fundamental biochemical variation associated with each such gene. Metabolic abnormalities associated with the gene for Fanconi's anemia (FA) may be investigated in skin fibroblast cell cultures, since it is known that the cultures differ from normal controls in several important characteristics. Systematic studies of FA fibroblast cultures may direct further studies toward elucidating the fundamental biochemical defect determined by the FA gene. An improved understanding of the metabolic effects of the FA gene will be of value in clarifying how this gene predisposes to cancer and leukemia.